Unilateral lymphadenitis caused by community-associated methicillin-resistant Staphylococcus aureus ST834 strain.

Community-associated methicillin-resistant Staphylococcus aureus (CA-MRSA) is a global concern, primarily as a cause of skin and soft tissue infections, particularly in young people. Here, we describe a case of unilateral multiple lymphadenitis caused by the CA-MRSA sequence type (ST) 834 strain. A previously healthy 15-year-old girl was referred to our hospital with fever and swollen lymph nodes in the right axillary, cubital, and groin regions. Imaging examinations revealed enlargement of the lymph nodes in these areas but no swelling in any other lymph nodes. The patient had self-destructive lymph nodes in her groin. MRSA was detected in all swollen lymph node samples. Antimicrobial susceptibility tests showed that MRSA was susceptible to clindamycin and levofloxacin, leading to the suspicion of CA-MRSA. Genetic analysis revealed that all strains were ST834 and carried the staphylococcal cassette chromosome mec IV and the toxic shock syndrome toxin-1 gene but not the Panton-Valentine leukocidin gene. The patient was treated with linezolid followed by oral clindamycin. This was a rare case of unilateral multiple lymphadenitis caused by ST834 CA-MRSA. Although ST834 strains are rarely reported, lymphadenitis has been frequently reported and is considered more likely to cause lymphadenitis than other CA-MRSA strains.

Surveillance of antimicrobial awareness among patients visiting community pharmacies.

OBJECTIVE: Although antimicrobial resistance (AMR) measures have been progressing, cases of patients requesting their doctors to prescribe antimicrobial agents and patients mistakenly believing that these agents are effective against viruses occasionally occur. In the AMR action plan (2023-2027) in Japan, one of the primary goals are public awareness and education. However, public understanding of AMR and antimicrobial agents has been reported to be at an unsatisfactory level. Here, we conducted a surveillance of antimicrobial awareness among patients visiting community pharmacies. MATERIAL AND METHODS: A questionnaire survey was conducted among patients visiting nine pharmacies in Hachioji, Tokyo, Japan. A total of 1887 active questionnaires were collected. The relationship between answers was analyzed using logistic regression analysis. RESULTS: Of the patients, 72% were unaware of AMR, and 68% believed that antimicrobials are effective against viruses. In addition, 28% of the patients answered that they did not take antimicrobial agents as prescribed by their physicians. Seventeen percent of the patients had never received appropriate instruction of antimicrobial use from pharmacists. Analysis of the relationship between answers showed that patients with correct knowledge were 1.65 times more likely to take antimicrobial agents as prescribed by their physicians (P < 0.01). Furthermore, the factors that led to the inappropriate behaviors of patients were associated with preliminary antimicrobial prescriptions from physicians (odds ratio, 3.18; 95% CI, 2.12-4.76) (P < 0.01). CONCLUSION: This study strongly suggests that physician and pharmacist interventions regarding the appropriate use of antimicrobial agents are important to improve awareness of antimicrobial agents.

Recyclable 2-Fluoropyridine Derivative as a Storage for Highly Electrophilic 1,1-Bis(triflyl)ethylene.

As an easy-to-handle reagent for the in situ generation of outstandingly electrophilic Tf2C=CH2 (Tf=CF3SO2), we have designed and synthesised a novel 4-substituted 2-fluoropyridinium zwitterion, in which a partially fluorinated alkyl group is attached to the pyridinium 4-position. Its zwitterionic nature has been well characterised by quantum chemical bonding analysis. By using this reagent, a wide variety of organic compounds, including commercial bioactive agents, were successfully decorated by the strongly acidic or ionic functionality. Remarkably, the 4-substituted 2-fluoropyridine derivative, which results from the zwitterion with the generation of Tf2C=CH2, can be rapidly separated and recovered from the reaction mixture appropriately using distillation, organic solvent extraction, or fluorous solid phase extraction techniques. Such multi-optionality for the purification methods favours in the isolation of the strongly acidic and/or ionic products.

The emerging threat of methicillin-resistant Staphylococcus aureus (MRSA) clone ST22-PT, carrying both Panton-Valentine leucocidin and toxic shock syndrome toxin 1 genes.

OBJECTIVES: Some MRSA strains produce Panton-Valentine leucocidin (PVL) and/or toxic shock syndrome toxin 1 (TSST-1), which are associated with severe infectious diseases. Although PVL- or TSST-1-positive strains have been isolated worldwide, strains carrying both PVL and TSST-1 genes are rare and sporadic. The objective of this study was to characterize these strains from Japan. METHODS: A total of 6433 MRSA strains isolated in Japan between 2015 and 2021 were analysed. Molecular epidemiological and comparative genomic analyses were conducted on PVL- and TSST-1-positive MRSA strains. RESULTS: A total of 26 strains from 12 healthcare facilities were PVL positive and TSST-1 positive, and all were classified as clonal complex (CC) 22. These strains exhibited similar genetic features to each other and were named as ST22-PT according to a previous report. Twelve and one of the ST22-PT strains were identified in patients with deep-seated skin infections and toxic shock syndrome-like symptoms, which are typical clinical features of PVL-positive and TSST-1-positive Staphylococcus aureus, respectively. Whole-genome comparative analysis revealed that the ST22-PT strains were highly similar to PVL- and TSST-1-positive CC22 strains isolated in several countries. Evaluation of the genome structure showed that ST22-PT possessed ΦSa2 harbouring PVL genes and a unique S. aureus pathogenicity island harbouring the TSST-1 gene. CONCLUSIONS: ST22-PT strains have recently emerged from several healthcare facilities in Japan, and ST22-PT-like strains have been identified in several countries. Our report highlights that the risk of international spread of PVL- and TSST-1-positive MRSA clone ST22-PT needs to be further investigated.

Contribution of amino acid substitutions in ParE to quinolone resistance in Haemophilus haemolyticus revealed through a horizontal transfer assay using Haemophilus influenzae.

BACKGROUND: In 2019, a high-level quinolone-resistant Haemophilus haemolyticus strain (levofloxacin MIC = 16 mg/L) was isolated from a paediatric patient. In this study, we aimed to determine whether the quinolone resistance of H. haemolyticus could be transferred to Haemophilus influenzae and to identify the mechanism underlying the high-level quinolone resistance of H. haemolyticus. METHODS: A horizontal gene transfer assay to H. influenzae was performed using genomic DNA or PCR-amplified quinolone-targeting genes from the high-level quinolone-resistant H. haemolyticus 2019-19 strain. The amino acids responsible for conferring quinolone resistance were identified through site-directed mutagenesis. RESULTS: By adding the genomic DNA of H. haemolyticus 2019-19, resistant colonies were obtained on agar plates containing quinolones. Notably, H. influenzae grown on levofloxacin agar showed the same level of resistance as H. haemolyticus. Sequencing analysis showed that gyrA, parC and parE of H. influenzae were replaced by those of H. haemolyticus, suggesting that horizontal transfer occurred between the two strains. When the quinolone-targeting gene fragments were added sequentially, the addition of parE, as well as gyrA and parC, contributed to high-level resistance. In particular, amino acid substitutions at both the 439th and 502nd residues of ParE were associated with high-level resistance. CONCLUSIONS: These findings indicate that quinolone resistance can be transferred between species and that amino acid substitutions at the 439th and 502nd residues of ParE, in addition to amino acid substitutions in both GyrA and ParC, contribute to high-level quinolone resistance.

Prevalence of antimicrobial-resistant Cutibacterium isolates and development of multiplex PCR method for Cutibacterium species identification.

INTRODUCTION: Cutibacterium species such as C. acnes, C. avidum, and C. granulosum are known anaerobic skin inhabitants and often cause surgical site infections. These species are genetically similar and are difficult to identify rapidly. In addition, their pathogenicity and antimicrobial resistance remain unknown. In this study, antimicrobial resistance in Cutibacterium isolates was studied and a multiplex PCR method for their identification was developed. METHODS: A total of 497 C. acnes, 71 C. avidum, and 25 C. granulosum strains which were isolated from the acne pustule and infectious regions, were used. RESULTS: The antimicrobial resistance rates of C. acnes, C. avidum, and C. granulosum strains isolated from patients with acne vulgaris were higher than those of strains isolated from patients with infectious diseases. In particular, macrolide-clindamycin-resistant strains were isolated most frequently from all species. Among the resistant strains, strains with 23S rRNA mutations were the most common in C. acnes (24.3%, 71/292), whereas C. avidum and C. granulosum strains were most frequently found with erm(X). For the first time, a C. granulosum strain carrying pTZC1, which codes erm(50) and tet(W), was isolated from patients with acne vulgaris. Regarding the rapid identification of causative pathogens from infectious regions, three Cutibacterium species were identified with 100% sensitivity and specificity using multiplex PCR method. CONCLUSIONS: Our data showed that antimicrobial resistance differed among Cutibacterium species. The multiplex PCR method may contribute to the rapid detection of Cutibacterium species and selection of appropriate antimicrobial agents.

High-Level Quinolone-Resistant Haemophilus haemolyticus in Pediatric Patient with No History of Quinolone Exposure.

The prevalence of antimicrobial resistance among Haemophilus spp. is a critical concern, but high-level quinolone-resistant strains had not been isolated from children. We isolated high-level quinolone-resistant H. haemolyticus from the suction sputum of a 9-year-old patient. The patient had received home medical care with mechanical ventilation for 2 years and had not been exposed to any quinolones for >3 years. The H. haemolyticus strain we isolated, 2019-19, shared biochemical features with H. influenzae. However, whole-genome analysis found this strain was closer to H. haemolyticus. Phylogenetic and mass spectrometry analyses indicated that strain 2019-19 was in the same cluster as H. haemolyticus. Comparison of quinolone resistance-determining regions showed strain 2019-19 possessed various amino acid substitutions, including those associated with quinolone resistance. This report highlights the existence of high-level quinolone-resistant Haemophilus species that have been isolated from both adults and children.

Quinolone Resistance Is Transferred Horizontally via Uptake Signal Sequence Recognition in Haemophilus influenzae.

The presence of Haemophilus influenzae strains with low susceptibility to quinolones has been reported worldwide. However, the emergence and dissemination mechanisms remain unclear. In this study, a total of 14 quinolone-low-susceptible H. influenzae isolates were investigated phylogenetically and in vitro resistance transfer assay in order to elucidate the emergence and dissemination mechanisms. The phylogenetic analysis based on gyrA sequences showed that strains with the same sequence type determined by multilocus sequence typing were classified into different clusters, suggesting that H. influenzae quinolone resistance emerges not only by point mutation, but also by the horizontal transfer of mutated gyrA. Moreover, the in vitro resistance transfer assay confirmed the horizontal transfer of quinolone resistance and indicated an active role of extracellular DNA in the resistance transfer. Interestingly, the horizontal transfer of parC only occurred in those cells that harbored a GyrA with amino acid substitutions, suggesting a possible mechanism of quinolone resistance in clinical settings. Moreover, the uptake signal and uptake-signal-like sequences located downstream of the quinolone resistant-determining regions of gyrA and parC, respectively, contributed to the horizontal transfer of resistance in H. influenzae. Our study demonstrates that the quinolone resistance of H. influenzae could emerge due to the horizontal transfer of gyrA and parC via recognition of an uptake signal sequence or uptake-signal-like sequence. Since the presence of quinolone-low-susceptible H. influenzae with amino acid substitutions in GyrA have been increasing in recent years, it is necessary to focus our attention to the acquisition of further drug resistance in these isolates.

Alternative quinolone-resistance pathway caused by simultaneous horizontal gene transfer in Haemophilus influenzae.

BACKGROUND: Quinolone-resistant bacteria are known to emerge via the accumulation of mutations in a stepwise manner. Recent studies reported the emergence of quinolone low-susceptible Haemophilus influenzae ST422 isolates harbouring two relevant mutations, although ST422 isolates harbouring one mutation were never identified. OBJECTIVES: To investigate if GyrA and ParC from quinolone low-susceptible isolates can be transferred horizontally and simultaneously to susceptible isolates. METHODS: Genomic DNA was extracted from an H. influenzae isolate harbouring amino acid substitutions in both gyrA and parC and mixed with clinical isolates. The emergence of resistant isolates was compared, and WGS analysis was performed. RESULTS: By adding the genomic DNA harbouring both mutated gyrA and parC, resistant bacteria exhibiting recombination at gyrA only or both gyrA and parC loci were obtained on nalidixic acid and pipemidic acid plates, and the frequency was found to increase with the amount of DNA. Recombination events in gyrA only and in both gyrA and parC occurred with at least 1 and 1-100 ng of DNA, respectively. The genome sequence of a representative strain showed recombination events throughout the genome. The MIC of quinolone for the resulting strains was found to be similar to that of the donor. Although the recombination efficacy was different among the various strains, all strains used in this study obtained multiple genes simultaneously. CONCLUSIONS: These findings indicate that H. influenzae can simultaneously obtain more than two mutated genes. This mechanism of horizontal transfer could be an alternative pathway for attaining quinolone resistance.

Molecular characterisation of carbapenem- and tigecycline-resistant Klebsiella pneumoniae strains isolated from blood and bile samples.

INTRODUCTION: The number of carbapenem-resistant Klebsiella pneumoniae (CRKP) strains are increasing, further raising healthcare concerns worldwide. In this study, we isolated three CRKP strains from bile and blood samples of an elderly patient (90s) with acute cholangitis and characterised the features and antimicrobial resistance mechanism of CRKP isolates. METHODS: Three CRKP isolates were characterised by Pulsed-field gel electrophoresis (PFGE), whole genome sequencing using the NovaSeq 6000, and antimicrobial susceptibility testing. Transcriptional levels of resistance-associated genes were measured by real-time RT-qPCR. RESULTS: PFGE analysis revealed highly similar patterns for these isolates. Furthermore, they showed resistance to not only carbapenem but also tigecycline. Genomic analysis of the blood isolate identified the exogenous resistance genes blaCTX-M14, tet(A), tet(D), opxAB, and qnrS1 but not any carbapenemase-encoding genes. In addition, nonsense mutations were found in both the outer membrane protein K36 (ompK36) and transcriptional regulator ramR, suggesting that this isolate developed multidrug resistance by acquiring both exogenous resistance genes and nonsense mutations. The extended-spectrum ß-lactamase-producing carbapenem-susceptible K. pneumoniae isolate exhibited the same susceptibility pattern, except to ß-lactams, as prior CRKP isolates. CONCLUSIONS: Antimicrobial susceptibility to carbapenem and tigecycline should be continuously monitored, because it might change from susceptible to resistant during another antimicrobial treatment, even if an isolate initially shows susceptibility, and the patient has not been exposed to these agents.

A case of Shewanella algae-induced bacteremia in Japan: Case report and literature review.

Shewanella algae (S. algae) is a rare bacterium that causes infectious diseases in humans. Herein, we present a case of an 84-year-old man with S. algae-induced bacteremia and performed a review of 12 cases identified via a literature search and this case. Literature review of previous reports in Japan have revealed that 69.2% of patients with S. algae-induced bacteremia had a history of contact with fresh fish. Appropriate interviews of patients, especially in the hot season, and the accurate identification of the causative bacterium, by using techniques such as MALDI-TOF-MS and genetic testing, are necessary if S. algae or other bacteria from the genus Shewanella are detected in blood-culture tests.

Escherichia coli GyrA Tower Domain Interacts with QnrB1 Loop B and Plays an Important Role in QnrB1 Protection from Quinolone Inhibition.

The Qnr pentapeptide repeat proteins interact with DNA gyrase and protect it from quinolone inhibition. The two external loops, particularly the larger loop B, of Qnr proteins are essential for quinolone protection of DNA gyrase. The specific QnrB1 interaction sites on DNA gyrase are not known. In this study, we investigated the interaction between GyrA and QnrB1 using site-specific photo-cross-linking of QnrB1 loop B combined with mass spectrometry. We found that amino acid residues 286 to 298 on the tower domain of GyrA interact with QnrB1 and play a key role in QnrB1 protection of gyrase from quinolone inhibition. Alanine replacement of arginine at residue 293 and a small deletion of amino acids 286 to 289 of GyrA resulted in a decrease in the QnrB1-mediated increase in quinolone MICs and also abolished the QnrB1 protection of purified DNA gyrase from ciprofloxacin inhibition.

Cutibacterium acnes phylogenetic type IC and II isolated from patients with non-acne diseases exhibit high-level biofilm formation.

Cutibacterium (formerly Propionibacterium) acnes is an important for not only exacerbating factor of acne vulgaris but also pathogen of surgical site infections (SSIs) in orthopedics and plastic surgery. Although biofilm-forming (BF) C. acnes are associated with intractable SSI, characteristics of these strains were still unknown. Here, we explored detailed molecular epidemiological features of BF C. acnes isolated as causative pathogen of infectious diseases. Phylogenetic types of 205 C. acnes strains isolated between 2013 and 2018 from 18 clinical departments of a university hospital in Japan were determined by single-locus sequence type (SLST). Clade H (traditional type IC) and K (type II) which are less relevant with healthy skin and acne vulgaris, were detected in 26.8% (55/205) and 16.1% (33/205) of the strains, respectively. The incidence of them was significantly higher than that of acne patients (H and K, each 2.9%, P < 0.05). In addition, SLST distribution of C. acnes strains differed by each department and isolation site. When biofilm formation was quantified, 51 strains (24.9%) were defined as high-BF strains. Notably, most high-BF strains were classified into the strains of clade H (56.4%, 31/55) and clade K (54.4%, 18/33), and these strains were frequently found in the strains isolated from patients of medical emergency center and plastic surgery. Similarly, high-BF strains were frequently found among the isolates from blood (35.7%) and catheters (30.0%), with a high proportion belonging to clades H and K. Compared to C. acnes strains isolated from acne patients, antimicrobial-resistant strains were less identified in non-acne patients. Our findings showed that pathogenicity of C. acnes strains differs by their phylogenetic types. Furthermore, we showed clade H and K have the ability of high biofilm formation and suggest that these strains have potential to become a risk factor for SSI.

Dissemination of quinolone low-susceptible Haemophilus influenzae ST422 in Tokyo, Japan.

INTRODUCTION: Haemophilus influenzae with a reduced susceptibility to quinolones (quinolone low-susceptible H. influenzae) has recently emerged in Japan. In addition, the regional outbreak of the quinolone low-susceptible H. influenzae ST422 clone has been reported. In this study, we isolated this clone from an acute care hospital located in a geographically different area from the previous outbreak and characterised the nature of this clone. METHODS: Eighty-nine H. influenzae isolated between 2017 and 2019 were tested. The antimicrobial susceptibility was determined by the broth dilution method. The genetic background was analysed by pulsed-field gel electrophoresis (PFGE) and multilocus sequence typing. Growth ability and ß-lactamase acquisition were evaluated by growth curve analysis and conjugative transfer experiments, respectively. RESULTS: Quinolone low-susceptible isolates accounted for 4.2% (1/24) in 2018 and 13.9% (5/36) in 2019. Most of the quinolone low-susceptible strains (83.3%) were classified as ST422 and had amino acid substitutions in quinolone resistance-determining regions in both GyrA and ParC. The patients' backgrounds were highly diverse. In addition, these isolates showed the same PFGE pattern as outbreak strains. The growth of ST422 clone was relatively faster than other clones. Furthermore, ST422 clone was able to acquire ß-lactamase from a ß-lactamase positive strain by horizontal transfer, becoming highly resistant to ß-lactams. CONCLUSION: Our study indicated that the quinolone low-susceptible H. influenzae ST422 clone has been spreading in the community undetected. In addition, this clone has the potential to grow faster and become more resistant through exogenous gene transfer. Therefore, ST422 clone should be monitored attention throughout Japan.

Antimicrobial activity and additive effect of the modified Gingyo-san with antimicrobials against Helicobacter pylori.

INTRODUCTION: Helicobacter pylori is an important factor in the development of gastroduodenal ulcers and gastric cancer. Although H. pylori eradication therapy has been employed, the eradication rate has decreased in recent years owing to an increase in clarithromycin-resistant strains. We previously reported the anti-infective effect of herbal medicines against several bacterial species. Here, we evaluated the growth inhibitory activity of herbal medicines alone and in combination with antimicrobials against H. pylori. METHODS AND RESULTS: Nine of 37 herbal medicines inhibited the growth of H. pylori ATCC700392. In particular, modified Gingyo-san showed the strongest growth inhibitory activity with a minimum inhibitory concentration (MIC) of 512 µg/ml for not only ATCC700392 but also clarithromycin-resistant strains having a 23 S rRNA mutation. Results of Time-Kill Kinetics Assay showed that 1 mg/mL modified Gingyo-san treatment for one hour killed 50% of the H. pylori population. Furthermore, modified Gingyo-san showed additive effects with clarithromycin, amoxicillin, and metronidazole against H. pylori ATCC700392 and clarithromycin-resistant strains. CONCLUSIONS: Our findings showed that modified Gingyo-san inhibits the growth of H. pylori and improves antimicrobial susceptibility when used in combination. Therefore, modified Gingyo-san has the potential to enhance the eradication rate of clarithromycin-resistant H. pylori.

Arthritis Caused by MRSA CC398 in a Patient without Animal Contact, Japan.

Clonal complex 398 methicillin-resistant Staphylococcus aureus (MRSA) is a typical lineage of livestock-associated MRSA. We report a case of intractable arthritis of the shoulder joint caused by a multidrug-resistant Panton-Valentine leukocidin-positive livestock-associated MRSA clonal complex 398 sequence type 1232 clone in a patient in Japan who had no animal contact.

Transferable Multidrug-Resistance Plasmid Carrying a Novel Macrolide-Clindamycin Resistance Gene, erm(50), in Cutibacterium acnes.

Antimicrobial-resistant Cutibacterium acnes strains have emerged and disseminated throughout the world. The 23S rRNA mutation and erm(X) gene are known as the major resistance determinants of macrolides and clindamycin in C. acnes We isolated eight high-level macrolide-clindamycin-resistant C. acnes strains with no known resistance determinants, such as 23S rRNA mutation and erm(X), from different acne patients in 2008 between 2013 and 2015. The aim of this study was to identify the novel mechanisms of resistance in C. acnes Whole-genome sequencing revealed the existence of a plasmid DNA, denoted pTZC1 (length, 31,440 bp), carrying the novel macrolide-clindamycin resistance gene erm(50) and tetracycline resistance gene tet(W). pTZC1 was detected in all C. acnes isolates (eight strains) exhibiting high-level macrolide-clindamycin resistance, with no known resistance determinants (MIC of clarithromycin, ≥256 µg/ml; clindamycin, ≥256 µg/ml). Transconjugation experiments demonstrated that the pTZC1 was horizontally transferred among C. acnes strains and conferred resistance to macrolides, clindamycin, and tetracyclines. Our data showed, for the first time, the existence of a transferable multidrug-resistant plasmid in C. acnes Increased prevalence of this plasmid will be a great threat to antimicrobial therapy for acne vulgaris.

A novel community-acquired MRSA clone, USA300-LV/J, uniquely evolved in Japan.

BACKGROUND: USA300 [ST8-staphylococcal cassette chromosome mec type IVa (ST8-IVa)/arginine catabolic mobile element (ACME) positive] is a major Panton-Valentine leucocidin (PVL)-positive community-acquired MRSA (CA-MRSA) clone. In Japan, we identified USA300-like strains with characteristics (ST8-IVc/ACME negative) similar to those of USA300. OBJECTIVES: To reveal the evolution of the USA300-like strains. METHODS: The whole-genome sequence of a USA300-like strain was determined and genome analysis was performed using Type Strain Genome Server, MUSCLE and progressiveMauve. RESULTS: Genome-based phylogenetic analysis showed that the USA300-like strain is more similar to the USA300-Latin American variant (USA300-LV), which is a PVL-positive CA-MRSA clone identified in South America, than to USA300. Instead of the ACME, copper and mercury resistance mobile elements were located on the genome of the USA300-like strain. In addition, the USA300-like strain possessed a unique mobile genetic element, ICE6013. Therefore, we named this novel USA300-LV variant identified in Japan as USA300-LV/J. CONCLUSIONS: Our findings strongly suggest that a PVL-positive CA-MRSA USA300-LV/J clone originating from abroad has uniquely evolved and disseminated in Japan.

An outbreak of severe infectious diseases caused by methicillin-resistant Staphylococcus aureus USA300 clone among hospitalized patients and nursing staff in a tertiary care university hospital.

The USA300 clone, which produces Panton-Valentine leukocidin (PVL), is a major highly pathogenic community-acquired methicillin-resistant Staphylococcus aureus (CA-MRSA) clone that is spreading throughout the world. Although the prevalence of the USA300 clone in Japan was very limited a decade ago, its incidence has been increasing in both community and hospital settings in recent years. There is great concern that the USA300 clone will cause more complicated diseases and become a serious threat to immunocompromised patients in hospital settings. Here, we report an outbreak of severe infectious diseases in a tertiary care university hospital involving the incidence of deep infections, including bacteremia, and continuous and frequent isolation of MRSA strains for five months from six patients and a healthy nursing staff member in the same ward. The genotype of all MRSA isolates was identical to that of the USA300 clone. Furthermore, pulsed-field gel electrophoresis analysis indicated that all MRSA had the same patterns. These data demonstrate that a USA300 clone outbreak had occurred in the hospital. Fortunately, this outbreak was terminated subsequent to the interventions of the infection control team and all patients recovered following the appropriate therapies. Our report demonstrates that patients carrying highly pathogenic CA-MRSA have the potential to become a source of nosocomial outbreaks that can spread to healthy healthcare workers. Therefore, stricter standard precautions should be applied for all patients at the time of admission to prevent such nosocomial outbreaks.

A risk as an infection route: Nasal colonization of methicillin-resistant Staphylococcus aureus USA300 clone among contact sport athletes in Japan.

Panton-Valentine leukocidin (PVL)-positive USA300 clone is a highly pathogenic and global epidemic community-acquired methicillin-resistant Staphylococcus aureus (CA-MRSA) clone. Athletes are particularly vulnerable to CA-MRSA infection because of the frequency of skin trauma, close-contact situations, and sharing of equipment that is customary in the athletic setting. We experienced a case of Japanese collegiate football player with septic pulmonary emboli secondary to infectious iliofemoral deep venous thrombosis caused by the USA300 clone. Here, we screened the nasal carriage of USA300 clone colonization among asymptomatic teammate of the patient to elucidate the infection route. Among 69 nasal samples, CA-MRSA strains were found in 5.8% (four samples). Molecular epidemiological analyses showed that three of the CA-MRSA strains were USA300 clone. Furthermore, pulsed-field gel electrophoresis revealed that all nasal USA300 clones showed 100% identity with the USA300 clone isolated from their teammate with critical infection. Our findings indicate that nasal colonization of the PVL-positive CA-MRSA, especially USA300 clone, pose a threat among contact sport athletes in Japan likewise other countries. An immediate infection control strategy for contact sport athletes is necessary to prevent outbreaks of PVL-positive CA-MRSA infections.